1. Technical Field
The present invention relates to a memory system, and more particularly, to a nonvolatile memory system and a block management method.
2. Related Art
Since a nonvolatile memory apparatus, specifically, a flash memory apparatus, has advantages of low power consumption, miniaturization, and low heat generation, it has been employed for various multimedia appliances including mobile appliances.
In the flash memory apparatus, data is recorded in units of block, where an operation for erasing a corresponding block is performed before the data is recorded, and such an erase operation is generally performed in units of page. If the erase operation is performed over a predetermined number of times, the corresponding block may degrade so as not to be available for any more erase cycles.
In general, the number of erasures of a single-level cell is limited to a hundred thousand and the number of erasures of a multi-level cell is limited to ten thousand. If the number of erasures of a specific block gets approximately to or exceeds the predetermined number, it is highly probable that a bad block occurs due to deterioration, resulting in the reduction of the lifespan of a memory system.
Therefore, in a nonvolatile memory system, all blocks of a memory area are equally used in order to maximally extend the lifespan of a memory apparatus. This is referred to as wear-leveling.
The basic concept of the wear-leveling is to distribute the use of blocks by replacing a physical block indicated by a logical block number. According to the simplest method, all memory blocks are sequentially used and then the first memory block is used again. However, since this method requires much time for block movement and erasure, the operation performance of a memory system may be degraded. Furthermore, if the number of memory blocks is increased, since the number of erasures required for the wear-leveling is also increased, much time is required for selecting a replacement block.